The Museum of History in the Japanese city of Otsu have for the first time, published the materials covering the investigation and trial in the 1891 assassination attempt on the heir to the Russian throne, Tsesarevich Nicholas Alexandrovich - the future Emperor Nicholas II, during his visit to Japan as part of his eastern journey.

The materials include 984 pages covering the trial of Tsuda Sanzo, as well as other artefacts related to the incident, including photographs and written testimonies.

The assassination attempt occurred on 11 May [O.S. 29 April] 1891, while Nicholas was returning to Kyoto after a day trip to Lake Biwa in Otsu. Tsuda Sanzo, one of his escort policemen swung at the Tsesarevich's face with a saber. The quick action of Nicholas's cousin, Prince George of Greece and Denmark, who parried the second blow with his cane, saved his life. Tsuda then attempted to flee, but two rickshaw drivers in Nicholas's entourage chased him down and pulled him to the ground. Nicholas was left with a 9 centimetre long scar on the right side of his forehead, but his wound was not life-threatening.

The assailant was arrested and imprisoned. The incident sparked a wave of remorse across Japan. Emperor Meiji publicly expressed sorrow at Japan's lack of hospitality towards a state guest, which led to an outpouring of public support and messages of condolences for the Tsesarevich. The Japanese emperor even traveled by train to Kyoto where he met with the Tsesarevich. The Tsesarevich received gifts, and more than 20 thousand telegrams of condolences and apologies from Japanese citizens.

The documents show that Tsuda remained silent throughout the trial. On the question of the motive behind the attack, he indicated only that the distinguished guest had showed a lack of respect to a monument erected in honour of the heroes of one of the samurai rebellion. Tsuda was sentenced to life imprisonment near Kushiro, Hokkaido , and died of an illness in September of the same year.